Please share what you're using as a power supply for you Benjolin, Zeitgeist, or both as an alternative to the 9 volt batteries. It'd be great if we included where we got them from and the cost as well.

Now for my question: Where did you get your bipolar 12V power supply? All I can find are kits or incredibly expensive bench monsters.

Danno Gee Ray wrote:

The Power Supply I'm using for my Benjolin is a surplus switching supply I picked up. It has +24VDC, +5VDC, +12VDC, and -12VDC outputs at various load capacities. The + - 12 VDC outputs are rated at 350 ma, and seem to be quite ample.

This looks like a pretty great option for experienced builders. (I don't have a sillyscope here though.)

oscilloclast wrote:

... I got my power supply in an old medical equipment enclosure that was provided at the Baltimore workshop (with Peter Blasser). Ken stone offers a board for a power supply (you'll have to order the parts from Mouser etc.). You can go to his web site "www.cgs.synth.net" and look for the "+/- 15 Volt Power Supply" which you can adapt to +/- 12 v (by changing the regulators).

David

David, I'm not sure if this is the one you are talking about, but it looks to be discontinued. I'm sure there is something else like it available though.

And for reference, specs from the man himself:

Rob wrote:

The Benjolin can run on a dual supply of +/-12V to +/18V, as it has its own +9V and -9V regulators on board. Optionally, 9V batteries can be connected after the regulators, which the regulators don't mind as long as there is ónly batteries or ónly a power supply connected! (Don't connect both batteries and a power supply at the same time to prevent possible explosion of the batteries!)
The Benjolin uses roughly 60mA of current.

The Zeitgeist has a +5V regulator that accepts a power supply voltage of +6V to +20V. It can easily share the +12V to +15V that also powers the Benjolin. The Zeitgeist uses roughly between 20mA and 40mA of current, depending on the delaytime.

I just received a 25W AC - DC Triple Output desktop power supply from Jameco. http://www.jameco.com/ made by MEAN WELL, Model: P25A13D-R1B. Data sheet at https://www.jameco.com/Jameco/Products/ProdDS/190960.pdf. I intend to power both my Benjolin and Zeitgeist from this AC-DC supply. I also ordered the 5 pin female DIN connector from Jameco-- take a look at either Jameco part number 15844 or 29399. They were cheap enough that I ordered one of each to have a choice for the final install. At this writing Jameco has more of these power supplies in stock and Jameco prices are the lowest, and shipping w/in USA is good.

Below I cut-n-paste as email (Nov 8, 2009) from Rob to myself and others which talks about power supplies:

Hi all,

My recommendations for a power supply for both the Benjolin and the
Zeitgeist.

Principally I do always recommend a desktop Plug-In AC Adapter power supply similar in looks to the ones used for laptops. These are the safest devices to use in terms of hazard of electrical shock. Regrettably they are a bit hard to find. But note that if you want to do circuit bending experiments,
especially when they involve body contacts, then *always* use batteries!

(Regrettably it seems to be a non-stocked item and might have a delivery
time of perhaps up to ten weeks.)

A simple 5-pole female DIN connector can be used on the enclosure of a
project to connect to this power supply. By using two female connectors on
the back of every enclosure one can daisy chain the power to perhaps five to
ten more boxes. Desktop power supplies are the easiest to share amongst
several projects, which is a definitive additional value.

This is also a very good alternative to a desktop supply when putting this
supply into its own plastic housing with several connectors to power several
projects at once, thus turning it into a desktop power supply all by itself.
Probably this power supply is the easiest available one, and so you might
consider it if you do not succeed to find a suitable desktop power supply.

but I do *not* recommend an open frame power supply for ány DIY project,
simply as the maybe twenty bucks extra that you pay for a closed frame
supply or thirtyfive bucks extra for a desktop power supply are peanuts when
at a moment in the future it does actually protect you from electrical shock
and saves your life! Néver take any risk with AC power!!!

The Meanwell P25A13D-R1B external PSU is my personal first choice.
http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=190960
The P50A13D-R1B can give more power if you need to run several boxes on the same supply. Both adapters have very good short circuit protection, if too much current is drawn they neatly shut off completely.
Additionally, in the EU one doesn't have CE issues when using an external desktop supply.
Only possible disadvantage of these adapters is that they use the same DIN plug as a MIDI connection, which might cause confusion on a box that also has MIDI in and outputs.

The Meanwell T40B is a perfect choice to build into a small to medium sized cabinet. Note that this one spreads its available power over the outputs used, so when +5V is not used the +/-12V outputs can source more current.

With switching power supplies one has the advantage of being able to use them all over the world. But analog audio circuitry needs extra analog regulators like 78Lxx and 79Lxx on the PCBs to smooth out the slight high frequency noise from the switching supply.

On bigger systems I use +/-9V regulators on each board/module. I often combine analog circuitry with CMOS (the max 20V type) and with the +/-9V I can run the CMOS on 18V, so I don't have to use voltage translation circuitry all the time between the CMOS and analog stuff. This also eliminates any crosstalk between modules over the power supply lines. With a T40B I can easily power like eight to ten analog modules. (And my modules are a bit more complex than usual.)

I put +12VDC to the 9VDC header on the Zeitgeist and the green power LED glowed yellow very bright so that I was immediately alarmed and unplugged the power. In the NYC:Harvestworks November 2009 workshop there were some questions about the quality of one of the chips provided with the Zeitgeist kit.

Has anyone had a chance to put that chip to the test on oscilloscope?

What is a good procedure and steps to follow when I try and power up the Zeitgeist the next time?

My solution has been to buy Behringer PSU6 14.8V AC wall adapters (cost EUR 25), and then use an AC/DC converter board inside the case (additional EUR 10). I change the plug at the instrument end from flimsy minDIN to something more sturdy. This works rather well, except when I need to make one for someone in the States, then I need to send them the new plug style and wiring instructions.

Does anyone have a source for a *switching* AC/AC adapter? Maybe one with a swappable mains plug? Or even European sources for the Meanwell adapters that Rob mentioned?

Internal PSU is Velleman K8042 Symmetric 1A Power Supply, takes 14.8 AC from Behringer PSU and makes 12V DC which goes on to the Benjolin. I know this is an extra step, but finding a portable bipolar power supply isn't that easy (so far only one has appeared in the many threads about Benjolins) and importing from the USA is getting more expensive all the time. Hope this info helps someone with parts which are easily obtainable in Europe._________________Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
macumbista.net

Although the power might not be as clean as from the Behringer three pole, center tapped transformer. Anyone else have an opinion on this?_________________Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
macumbista.net

A friend and I worked out a simpler, smaller, one-sided and etchable PCB for the MFOS wall wart power supply for use with the Benjolin.

The Benjolin requires a very small amount of current, so one large cap per rail is enough. In fact, although 3300uF is listed, I have been using 2200uF caps (which aren't quite as tall and fit better into smaller enclosures) with no noticeable difference. Large caps should have 7.5mm lead spacing.

Resistors are 2K4 or 2K2, only to provide small load so that the PSU output can be measured without hooking it up to your Benjolin. Small caps are 1uF tants, diodes are 1N4004 and voltage regulators are LM7812 and LM7912. Circuit is fed with a 12V AC wallwart and outputs +12V/-12V DC. Pls ignore the "R" markings for the diode ring and use the markings on the drawings of the diodes themselves. See the MFOS site for full details.

Here is the copper (not mirrored) and parts overlay. Board size is 51mm x 78mm, PNG is at 150 DPI. You should know what to do with it from there...

I did build a simple power supply using the LT 1054 voltage converter for my Benjolin. It's very small, and costs around 6€ in parts. The converter generates the negative supply so you can use any single voltage wall wart (>=11V).
Already built it for 2 Benjolins and I didn't notice any drawbacks.

A 9v regulator needs 12v input minimum (the doubler probably also)...
Of course you could use +/-9v unregulated to begin with but you would need supply decoupling caps (unregulated means much more ps ripple from the rectified ac supply), or use two 9v batteries like Rob proposes (batteries have no ripple).

The regulators may help also with the square wave/pulse currents from the oscillators and cmos, that pollute the supply rails and cause crosstalk.

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